Flip-chip solder bump bonding of GaAs-based devices onto silicon integrated circuits (ICs) is known. See, for instance, K. W. Goossen et al., IEEE Photonics Technology Letters, Vol. 7(4), pp. 360-362, 1995.
If the GaAs-based devices are optoelectronic devices, then it is frequently necessary to remove the GaAs substrate to provide optical access to the devices. This is, for instance, the case in Gs/AlGaAs multi-quantum well (MQW) detector/modulator diode arrays that are flip-chip solder bump bonded onto a silicon CMOS chip. See, for instance, K. W. Goossen et al., IEEE Photonics Technology Letters, Vol. 5(7), pp. 776-778, 1994.
The conventional method of making the diode array involves providing a device structure that comprises a thick (e.g., about 1.5 .mu.m) Al.sub.0.3 Ga.sub.0.7 As etch stop layer for GaAs substrate removal. See, for instance, U.S. Pat. No. 5,385,632 to K. W. Goossen. However, the conventional method is not fully satisfactory. Due typically to relatively low etching selectivity between GaAs and Al.sub.0.3 Ga.sub.0.7 As, the removal of the GaAs substrate by etching frequently is plagued by non-uniformity problems, including missing devices at and near the edges of the arrays. This loss of devices from the edges of arrays is typically not acceptable, and typically requires limitation of the size of the arrays.
A method of making a GaAs/based opto-electronic device (especially arrays of such devices) that can readily facilitate uniform removal of the GaAs substrate would be desirable. This application discloses such a method.
It is known that InGaP can serve as an etch stop layer for GaAs, and some chemical etchants that exhibit selectivity between InGaP and GaAs are known. See, for instance, T. Shitara et al., Journal of Crystal Growth, Vol. 150, No. 1-4, Part 2, pp. 1261-1265 (May 1995), and J. R. Lothian et al., J. of Electronic Materials, Vol. 21(4), pp. 441-445, 1992. However, conventional usage of InGaP etch stop layers is for removal of relatively thin (typically .ltorsim.2 .mu.m) layers of GaAs, and removal of relatively thick (typically .gtorsim.100 .mu.m) layers of GaAs over InGaP has, to the best of our knowledge, not been suggested previously.